1. Field of the Invention
The present invention generally relates to infrared imaging devices, and more particularly, to an infrared imaging device, including an infrared detector, a view switching function, and a sensitivity correction function.
2. Description of the Related Art
An infrared imaging device is, for instance, mounted on an airplane and used for recognizing an objective body on the ground or in the air. It has been required that an image taken by the infrared imaging device be of high quality and that the infrared imaging device be small and lightweight.
In addition, the infrared imaging device requires a view switching function and a sensitivity correction function.
Plural kinds of magnification lenses having different magnifications are switched on an optical axis by the view switching function of the infrared imaging device. Generally, the objective body is initially detected by a magnification lens having a low magnification. And then, the magnification lens having a low magnification is replaced by a magnification lens having a high magnification by the view switching function and thereby the objective body is recognized and distinguished.
Furthermore, dispersions of respective sensitivities of a great number of pixels comprising infrared detect elements are detected and corrected electrically by the sensitivity correction function. The quality of the image taken by the infrared imaging device may be improved by implementing the sensitivity correction as required.
FIG. 1A is a plan view of a related infrared imaging device 10. FIG. 1B is a section taken on line axe2x80x94a in FIG. 1A. FIG. 1C is a section taken on line bxe2x80x94b in FIG. 1A. FIG. 2 is a schematic illustration of the related infrared imaging device 10. Referring to FIGS. 1A through 1C and 2, the infrared imaging device 10 includes a housing 11, an objective lens 12, a varying magnification lens 13, an infrared detector 14, a view switching mechanism 20, and a sensitivity correction mechanism 30. The objective lens 12, the varying magnification lens 13, and the infrared detector 14 are arranged in the line of an optical axis 15. The objective lens 12 is mounted on an upper surface of the housing 11. The varying magnification lens 13, the infrared detector 14, the view switching mechanism 20, and the sensitivity correction mechanism 30 are provided inside of the housing 11.
As shown in FIG. 2, an infrared light 16 radiated from the objective body is received by the objective lens 12 and the varying magnification lens 13 and reaches the infrared detect element 50 in the infrared detector 14. As a result, the infrared light 16 is focused into an image of the objective body on the infrared detect element 50. An output from the infrared detect element 50 is amplified and transmitted to the indication part 60. The image formed by the infrared imaging device is projected on the indication part 60.
The view switching mechanism 20 is supported in a state where the view switching mechanism 20 can be moved in the X1-X2 direction as shown in FIG. 1A. The view switching mechanism 20 includes a mount board 22, a motor 23 and a crank mechanism 24. The varying magnification lens 13 having a low magnification and the varying magnification lens 21 having a high magnification are mounted on the mount board 22. The mount board 22 can be moved in the X1-X2 direction by using the crank mechanism 24 driven with the motor 23.
The sensitivity correction mechanism 30 has a sensitivity correction base 33 and a motor 34. The sensitivity correction base 33 having a fan shape is supported by an output shaft 32 of a gear mechanism 31. The gear mechanism 31 is driven by the motor 34. A standard heat source board 35 of a normal temperature side and a mirror 36 as a standard heat source board of a low temperature side are provided on a lower surface of the sensitivity correction base 33. The sensitivity correction base 33 is arranged in a space 40 between the varying magnification lens 13 and the infrared detector 14.
The infrared detect element 50 is provided inside of the infrared detector 14. The infrared detect element 50 has a structure in which a great number of pixels are arranged in a matrix shape and is cooled cryogenically by a cooler not shown in FIGS. 1A through 1C and 2.
Sensitivity correction is implemented by utilizing the temperature of the infrared detect element 50 itself and a normal temperature. The motor 34 is driven and the sensitivity correction base 33 is rotated in the A-B direction shown in FIG. 1A by using the gear mechanism 31. First, the outputs of the respective pixels of the infrared detect element 50 are measured when the mirror 36 is moved onto the optical axis 15, and then the outputs are saved in digital form. Next, the standard heat source board 35 of the normal temperature side is moved onto the optical axis 15. Outputs of the respective pixels of the infrared detect element 50 are measured when an infrared light radiated from the standard heat source board 35 is received by the infrared detector 14, and then the outputs are saved in digital form. The sensitivity correction is implemented by reading out the saved information and calculating a correction coefficient. When the mirror 36 faces the infrared detector 14, the infrared detect element 50 is reflected in the mirror 36. Since the infrared detect element 50 is cooled cryogenically as described above, a cryogenically cooled infrared light radiated from the infrared detect element 50 is reflected by the mirror 36 and received at the infrared detect element 50.
The view switching is implemented by driving the motor 23 and moving the mount board 22 with the crank mechanism 24, and thereby the varying magnification lens 13 is displaced by a magnification lens 21 having a high magnification.
However, two motors are needed for the conventional infrared imaging device 10 because the conventional infrared imaging device 10 has the view switching mechanism 20 and the sensitivity correction mechanism 30 provided independently. Hence, it is difficult to miniaturize and reduce the weight of the infrared imaging device 10.
In addition, the sensitivity correction mechanism 30 has a structure in which the sensitivity correction base 33 is arranged in the narrow space 40 between the varying magnification lens 13 and the infrared detector 14. Therefore, it is difficult to provide a standard heat source having the sensitivity correction base 33 on which a peltier device is equipped. Rather, the standard heat source board 35 and the mirror 36 as the standard heat source board of a low temperature are provided on the sensitivity correction base 33 in the conventional infrared imaging device 10.
Accordingly, two kinds of standard temperature infrared lights, namely the infrared light radiated from the standard heat source board 35 and the infrared light cooled cryogenically, radiate to the infrared detect element 50. The difference of temperatures between the two kinds of standard temperature infrared lights provided to the infrared detect element 50 is 100 centigrade or more. Meanwhile, the objective body of the infrared imaging device 10 generates heat, and the objective body is detected with the infrared imaging device 10 by comparing a temperature in a background source with the objective body.
Furthermore, the sensitivity of the infrared detect element 50 is not proportional to the energy of the infrared light generated by the objective body. Rather, the infrared light has a property in that a secondary curved line can be drawn, wherein the energy of the infrared light is defined as the horizontal axis and the sensitivity of the infrared detect element 50 is defined as the vertical axis. Therefore, since the difference of temperatures of two kinds of standard temperature infrared light sources provided to the infrared detect element 50 of the conventional device is 100 centigrade or more, it is not possible to obtain a proper coefficient of the sensitivity correction by using the property of the sensitivity of the infrared detect element 50.
Hence, there may be a problem concerning the quality of the image taken by the infrared imaging device 10 and projected on the indication part 60.
Accordingly, it is a general object of the present invention is to provide a novel and useful infrared imaging device in which one or more of the problems described above are eliminated.
Another and more specific object of the present invention is to provide an infrared imaging device, including a board which is movable inside the infrared imaging device, plural kinds of magnification lenses, and plural kinds of infrared light radiation parts which radiate infrared lights having respective radiation temperatures, wherein the lenses and the infrared light radiation parts are situated on the board.
According to the present invention, it is possible to miniaturize and reduce the weight of the infrared imaging device, as compared to the conventional infrared imaging device having a board on which magnification lenses are mounted and a separate board on which infrared light radiation parts are mounted. In addition, it is possible to detect smaller differences regarding measurements of the infrared light radiation parts, and thereby the infrared light radiation parts can have a peltie device, for example. Furthermore, according to the present invention, it is possible to make 10 centigrade as the difference in temperature between the infrared light radiation parts of the high temperature side and the low temperature side. Because of this, it is possible to implement the sensitivity correction accurately.
The plural kinds of the infrared light radiation parts may be situated between the respective magnification lenses on the board and along a movement direction of the board.
According to the present invention, it is possible to implement a sensitivity correction of an infrared detect element of the infrared light radiation part during a view switching. Accordingly, whenever the view switching is implemented, the sensitivity correction is implemented. Hence, the accuracy of the sensitivity correction is improved, and thereby it is possible to provide a higher quality image.
The board may have a disk shape and the magnification lenses and the infrared light radiation parts may be arranged along an inner circumference of the board.
According to the present invention, it is possible to mount the magnification lenses and the infrared light radiation parts easily, and thereby it is possible to miniaturize the infrared imaging device. In addition, the movable board may have a tooth part, so that the movable board can be rotated by a gear of a small motor without a reduction gear motor unit.
The infrared light radiation parts may include a base part which is fixed to the board.
According to the present invention, it is possible to miniaturize the infrared light radiation parts because only one base part is used for mounting the infrared light radiation parts thereon.
The other object of the present invention is to provide an infrared imaging device having an infrared detector, including magnification lenses, and view switching means for switching from one of the magnification lenses to another magnification lens, sensitivity correction means for correcting a displacement of a sensitivity of the infrared detector, wherein the magnification lenses and the sensitivity correction means are situated on the view switching means.
Other objects, features, and advantages of the present invention will be more apparent from the following detailed description when read in conjunction with the accompanying drawings.